Rune by Zodiac

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds a billing trait with 'Cost: 10 credits (Tier 1)' and notes the POST endpoint, which is useful behavioral context beyond the annotations, though auth and rate-limit details are absent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The definition is short and front-loads the core mapping before compact metadata. The '[Required: sign]' line largely duplicates the schema's required field, so there is minor redundancy, but no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple one-enum lookup with rich annotations and an output schema, the description supplies the domain, required input, endpoint, and cost. The main missing element is explicit routing guidance against the many sibling rune tools, which the tool name only partially addresses.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, but the sole parameter is an enum of twelve zodiac signs. The description adds the meaningful qualifier that the sign is tropical, which is not in the schema, but it does not elaborate on format or selection beyond what the enum already shows.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The phrase 'Tropical-sign → Elder Futhark affinity rune' identifies a specific mapping from tropical zodiac signs to Elder Futhark runes. It is distinguishable from draw-style rune siblings by its zodiac input, but it never explicitly names or contrasts those alternatives, so it falls short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage by stating the required sign and the Elder Futhark group, so an agent can infer this is for looking up a rune affinity from a tropical sign. It does not state when to prefer this over runes_single, runes_three, runes_nine, or runes_runes, nor does it give exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.